Will / Can Increasing the Velosity Lesson Leading problems ?

[geo57]

I have heard this both ways from a variety of reputable sources, but thought I'd get some input from here. Can or will increasing the velosity of a given hard cast bullet actually lead a barrel less than a lower velosity loading ? I currently run a commercial, hard cast, 200 gr. RNFP bullet, sized .430 ( hardness factor not given & does not have a gas check ) from a .44 mag Ruger Super Blackhawk with 7.5 grs. of Unique that clocks about 900 FPS. Chamber mouths show no leading whatsoever, but the 1st inch or 2 of barrel shows light to moderate leading, nothing too bad . My question is this . If I wanted to push this same bullet, with 10 grs. of Unique for about 1100-1150 FPS, is it your opinion that the barrel leading would increase, decrease, stay the same, or are there too many variables to reach a conclusion without actually testing it ? I'd like a heavier load from this same bullet to compliment my lighter load, but at the same time don't want a heavily fouled barrel either . I have been reloading for almost 35 years, but have no experience pushing hard cast bullets beyond 900 FPS . Your thoughts , opinions, and experiences in these lines are appeciated. Thanks.

 

[rcmodel]

It is entirely possible that a hotter load would lead less, or not at all.
That your problem is with the first couple of inches of barrel indicates the hard bullets are not getting enough pressure to bump up to fit the cylinder throats.

So, you are getting gas blow-by melting the base or first driving band causing the leading.

Or, it could be the bullets aren't as hard as they would like you to believe, and are skidding before the rifling can get them up to rotational speed, which causes the leading, even at the low 900 FPS velocity.

Bottom line is, you are just going to have to try loading them hotter and see what happens in your gun.

 

[kragluver]

Leading from cast bullets is a function of several things (in this approximate order) -- (1) bullet fit to bore; (2) alloy hardness; (3) velocity; and (4) lube performance. I guess I should also add bore condition (rough bores could lead more). If you're shooting a commercial bullet, your only option is to probably play with the velocity as you suggested. However, I'd suggest that perhaps the bullet is not properly sized to the bore and this may be the real source of your problem. Have you slugged the barrel of your revolver? Bullet size should be at or 0.001" over bore diameter. Go here (http://www.lasc.us/ArticlesFryxell.htm) and read all of Glen Fryxell's articles. Most of the best info I've learned about casting and shooting cast came from these articles.

 

[rcmodel]

In a revolver, bullet size should match the throats.

The heck with the bore size.

If they don't fit the throats, or slug up to fit the throats, leading starts before they ever get a chance to fit the bore.

 

[454PB]

What rcmodel said. If the cylinder throats are either too big or too little, leading will result.

Too big allows hot gases to leak around the bullet base before it even reaches the forcing cone. Too small sizes the bullet down and the result is the same.

Ideally, using .430" bullets, the throats should be no larger than .430". If they are .431" or larger, then the bullets you are using are too small. The solution is to use a larger bullet, regardless of the bore size.

The symptoms you describe (leading in the first few inches of barrel) are classic symptoms of a bullet too small for the cylinder throats. The "bumping up" theory is weak. Yes, it can happen, but usually with very fast burning powders combined with maximum or near maximum loads. Not something I would depend upon for a magnum handgun load.

 

[geo57]

Thanks to all for your imput . FWIW, with the cylinder out of the frame, these bullets will not slide out the front of any of the chambers when slowly letting them slide in from the back. Only a small portion of the nose is visible. I'm hoping this may be a positive sign that the chamber mouths are not too big for the projectile in question. Thanks again.

 

[fecmech]

Geo--My Ruger SBH has .434 throats and will lead badly with a .430 bullet and loads in the 900-1000 fps range. The same bullet over a stiff charge of 296,AA9, or 2400 and clocking 1300 fps is lead free. In order to shoot the lighter loads in my SBH I have to size them to .433 and the leading disappears. I now size everything for that gun to .433 and the accuracy improved in the heavier loads. From what I've read over at Cast Boolits Ruger .44 throats run large.